This invention relates to a double hung or single hung window assembly fabricated from extrusions of rigid plastics material such as rigid polyvinyl chloride, and of the general type disclosed in U.S. Pat. No. 6,675,537 and No. 6,826,871 assigned to the assignee of the present invention, and the disclosures of which are herein incorporated by reference. In such window assemblies, and especially large window assemblies, the horizontal sash rail members are typically not sufficiently stiff to withstand the structural pressures resulting from high winds which occur, for example during a hurricane or tornado, and which tend to pull the fabricated sash frame and glass assembly out of the fabricated main frame assembly. Thus the sash frame members are commonly reinforced with stiffening bars or members which are configured to fit with minimum clearance inside the hollow sash rail members, for example, as disclosed in above-mentioned U.S. Pat. No. 6,826,871.
The vertically sliding window units of a single hung or double hung window assembly are also commonly designed so that the movable or operable sash frames can be disengaged from the outer main frame and then tilted inwardly of the building to provide access for cleaning the exterior surface of the glass window panel from the interior of the building. The tilt latches, such as disclosed in the above-mentioned patents and in other U.S. patents, are designed for releasably securing the upper sash rail of the operable sash frame in its normal operating position and may be released or disengaged for tilting the sash frame into the building. Sometimes, the tilt latch bolts may be integrated or connected to the sash frame security lock mechanism which are partially recessed within the upper rail of the movable sash frame, for example, as disclosed in U.S. Pat. No. 7,070,211.